This invention relates to a yieldable joint for connecting two cylindrical pipes, and more particularly to an improved yieldable joint for connecting pipes in a vertical exhaust stack such as commonly found on farm tractors, diesel trucks and other heavy equipment for conducting exhaust gases from the engine to a point above the top of the vehicle.
Low hanging overhead objects such as tree limbs and bridges are potential sources of damage to farm tractors, diesel engines and other heavy equipment because such objects are obstructions that are capable of contacting the vertically extending exhaust stacks of these vehicles. Exhaust stacks usually are not yieldable and, when struck by an overhead object, the exhaust pipe and the manifold to which it is attached may be damaged and require expensive repairs.
Ideally, an exhaust pipe that is high enough to strike an overhead object will yield during contact with the object and, after contact terminates, will automatically return to its normally vertical position without damage to the exhaust pipe, or the attached manifold, or the object. Moreover, the ideal yieldable exhaust stack will be capable of leaning in all directions (360.degree.)--forward, rearward, left, right or between--; and will embody a construction that is not susceptible to functional failure due to rust build up, vibrations or high temperatures.
Apparatus has been proposed for yieldable exhaust stack joints. U.S. Pat. No. 3,063,741 describes a yieldable joint for exhaust stacks that is designed to yield upon contact with an overhead object and that is capable of automatically returning the stack to its vertical position after contact with the obstruction has ceased. However, this stack is capable of yielding only in a direction or plane parallel to the direction of travel of the vehicle, i.e., forward or backward. Frequently, an exhaust stack must be capable of motion in directions other than parallel to the vehicle's direction of travel, particularly for vehicles such as farm tractors which are likely to encounter tree limbs that will urge the stack in a direction that is not parallel to the direction of motion of the tractor. Moreover, an asymmetrical object such as a tree limb may urge the stack successively in several different directions with respect to the stack's normally vertical position as the contact and relative motion between the stack and limb continues. In such a situation, this prior device, which is capable of yielding only in a single direction or plane, will not prevent damage to the vehicle or overhead object. Two other prior devices for providing a yieldable joint for exhaust pipes are described in U.S. Pat. No. 3,352,573 and U.S. Pat. No. 3,815,941. Similarly, both of these prior devices are capable of yielding only in a direction parallel to forward or backward motion of the vehicle; but they are not capable of yielding to prevent damage to the exhaust stack when an overhead object forces the stack in a direction other than parallel to the vehicle's direction of travel.